1. Field of the Invention
This invention relates to a lighting device using a board on which multiple light-emitting elements are arrayed.
2. Description of the Related Art
Lighting devices using light-emitting diodes (LED) are used instead of fluorescent lamps in various shapes such as fluorescent tube lamps and fluorescent ring lamps (Japanese Patent Application Publication Nos. 2008-176996 referred to as Patent Document 1 and 2012-160430 referred to as Patent Document 2, for example). As an example, Patent Document 1 proposes a lighting device in which a flexible printed circuit board with light-emitting elements mounted thereon is fixed to a base member. This lighting device includes: a base member formed in a stair shape with an alternating series of first faces directed in a first direction and second faces directed in a second direction; and a flexible printed circuit board attached on the first faces and the second faces of the base member along the stair shape of the base member. Furthermore, in the lighting device, light-emitting elements are mounted on the portions of the flexible printed circuit board on the first faces of the base member, while components other than the light-emitting elements are mounted on the portions of the flexible printed circuit board on the second faces of the base member.
As another example, Patent Document 2 proposes a lighting device. In this lighting device, a flexible printed circuit board (FPC) in which a copper-foil pattern (conductor) integrated with a film is further integrated with a flexible metal-made base to form a metal base FPC, and light-emitting elements and a lighting control circuit are provided to the metal base FPC. In the lighting device, the metal base FPC is bent while being kept away from a lamp body, and at least one attachment mechanism is provided to attach an end portion of the metal base FPC to the lamp body. Here, in the lighting device, the metal base FPC is integrated with the metal-made base along the shape of the stair-shaped metal-made base.
In the related lighting devices discussed above, the flexible printed circuit board is fixed to the base member or the metal-made base by being folded at an angle along the stair shape of the base member or the metal-made base. Such attachment work of the flexible printed circuit board requires time and efforts, and may cause a break in wirings in the flexible printed circuit board.
Furthermore, the light-emitting elements placed on the center side of the flexible printed circuit board are fixed at the center sides of the first faces of the base member or the metal-made base in the stair shape with treads and risers at right angle. With this construction, since the whole portions of the flexible printed circuit board on the first faces are exposed in the light-emission direction, the lighting devices as a whole is large in size.